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If the flashes of light were simultaneous in their frame. And you are assuming they are simultaneous in both frames. Neither do I. He stipulates elsewhere that the flashes are simultaneous for the embankment observer. Here, he is showing how they can't be simultaneous for the train observer. Note how Einstein is very careful to always note which frame he is talking in reference to: "... (considered with reference to the railway embankment) ...". There's no mistake. Each observer is entitled to think of themselves as at rest and the other as in motion. If talking from the point of view of the embankment there's no mistake to consider the train as moving. And Einstein makes no such assertion as you claim here. The flashes are in no way "in" or "more connected to" the embankment frame. Sorry, but I think your interpretation is very poor. I think you are tryting to hard to get to some conclusion you prefer. No. 1916 was nearly a hundred years ago. I really don't think you've stumbled on some mistake that 98 years of science has missed. (Yes, Argumentum ad populum is a fallacy). You've said this so many times I wonder if you are purposely being obstuse. He wrote: "Are two events (e.g. the two strokes of lightning A and B) which are simultaneous with reference to [ 31 ] the railway embankment also simultaneous relatively to the train?". You keep ommitting the "with reference to", implying that it's assumed the simultaenity is absolute. Only, if simultaenity is absolute, and that if two events are simultaneous in one frame they are simultaneous in all frames. If you assume that, not only are assuming the result you want (and in disagreement with Comstoicks result) but you are invalidating the postulates of SR. No. Sorry, you are deliberately missing the point in too many ways; I do not see your interpretation of Einstein as rational. That's way off in two ways. The first is you'll get a contradiction in reality. An observer can't both see the flashes at the same time and not see them at the same time. But that's the situation you are trying to create. Secondly, you stubbornly refuse to let go of the idea that simultaenity is absolute - even though you accept Comstocks result! Vice versa here means that events simultaneous in the train frame can't be in the embankment frame. They would of course have to be different events than two events that are simultaneous in the embankment frame. See the paragraph above. You're not far off here. I don't understand why you can't extend that idea. NO HE DOESN'T! See above. Until you let go of this, you won't understand the experiment, and you'll continue to need your "playing God" view.

Well, I don't think there's any need for lorentz, time dilation or length contraction in Einsteins version either. Nor do I think there's any ambiguity. That setup and stipulations are no different really (in the sense of setupishness and stipulationity) than the Einstein version. The setup by comstock ensures the flashes are simultaneous in the car frame, and shows they won't be for the bystander. Einstein sets up the embankment frame to have simultaneous flashes and shows they won't be simultaneous for the other observer. Well, I think he succeeded. It's easy to come up with ways section 9 could have been improved, but it stands alone. More or less. But: depending on the setup, and which frames the flashes are simultaneous in. Comstock set it up so the flashes will be simultaneous in the car frame, by placing the bulb in the centre of the car. Einstein stipulates the strikes to be simultaneous in the embankment frame. It's basically the same thing. The real point is - what now is the situation for the other frame? Aside from you seeming to contradict yourself (because the end result is the same but you claim different interpretations) that's where the Comstock experiment falls down, it doesn't show the reciprical nature of the relativity of simultaneity very well. I really don't see why you are so hung up on that claimed "ambiguity". Comstock made the flashes simultaneous for one observer. Einstein stipulated them to be for one observer. Meh! I don't think Comstocks is stronger. Here you are assuming your opinion to be universal. I don't think Comstock shows recpricity well. And, given neither of his observers are equidistant from the ends of the carriage (going by your diagram) then they both need to use distance and speed of light to figure out if the flashes were simultaneous (in their frame). Einstein does that better by having both of his observers equidistant from the strikes. Given you seem to accept Comstocks result, why do you phrase this as "that occurred at the same time" without reference to which frame they occured at the same time in? This where it seems you seem to assume absoluteness of simultaneity - and then get consfused by the results of the experiment! In the given scenario, yes. Well, that's basically getting to be metaphysical rubbish. Strikes are either going to be simultaneous in a frame or not. There's no "God power" involved in looking at a case where two strikes were simultaneous in one frame and figuring out whether they were in another. No more than Comstock is "God" with his light bulb placement. Let's have a thought experiment where a rock lands on my head, the question is: did the rock land on your head? We don't need to "play God" to say no. The rock just happened to land on my head not yours, whether in a thought experiment or in reality. If the flashes were simultaneous in their frame. (You continue to assume that simultaneous events must be simultaneous in all frames. (You show this in your 5(6) points reply to Studiot). You then deny the results of this thought experiment based on that assumption. It's your thinking that's circular. The experiment is much more fair than you. It simply chooses events which do happen to be simultaneous in one frame, and asks are they also simultaneous in the other frame? It doesn't assume they are not in the other (that would be circular), it shows they can't be.) No. All your "God stuff" totally misses the point. Can events be simultaneous? (Would you really say no?) Well, then lets take the case where they were simultaneous in frame A. Either you are going to demand that they were also simultaneous in all other frames, or, you can figure out if they would be simultaneous in those other frames. Same as Comstock did. I think I'm sitting still. An observer sitting still on Mars might think I'm moving very fast. Who is right? Do we need some "God" to step in and say who is right?

Myth 1: Free lunch.

Yes. In the paper he writes (my underlines): ... so I'm confident of my result, and attempt to explain it to you. You are over complicating it. You seem to be trying hard to have your own unique interpretation so that you can then claim some oodd result. The whole point of R.O.S. is that there is no absolute simultaenity. The thought experiment shows this by describing a scenario, with two frames, where the events are assumed to be simultaneous to be simultaneous in one frame, and showing they can't be simultaneous in the other. (If the result were that it was shown the events were also simultaneous in the other frame, the title of section nine would be different!) What you seem to want to do is stipulate that the strikes are simultaneous in both frames. That's such a wild (and circular) interpretation of the thought experiment I can't follow your reasoning. Note that the thought experiment doesn't stipulate that the strikes are not simultaneous in both frames. It shows how if they are in one, they won't be in the other. Yeah - so you are stipulating that they'll both consider the same two strikes as simultaneous. You are assuming the thing you want to be true. You are assuming absoluteness of simultaenity. Can you explain why and how your thought here could be correct? There is no preference! The strikes just happen to be simultaenious in one of the two frames. The experiment then shows (not assumes) they can't be in the other. (You could have a scenario where the strikes are not simultaneous in either frame. Even if you believe in "absolute simultaenity" that'd be a pretty pointless exercise!) Two other strikes might have been simultaenious in the train frame. Or neither frame! There is no absoluteness to simultaenity, there is no preference; no more than there is any preference to a rock landing on my head and not yours. I was just in the wrong place. It's not preference. In the end there are some things that are "absolute". One of these will be things that occur in one location, which here is the flahes reaching one observer. All observers will agree if the flashes strike one observer at the same time. That is something for which there will only be one truth. Einstein shows that if the flashes reach one observer (whichever) at the same time, they can't reach the other observer at the same time. That other observer can't disagree with that. He's in the same universe. The flashes won't reach him at the same time so they were not simultaneous in his frame. * note that he writes "Are two events (e.g. the two strokes of lightning A and B) which are simultaneous with reference to the railway embankment also simultaneous relatively to the train?". He's not saying, as you imply, that the events were simultaneous ... not in that absolute way. He's clear that he's talking about the embankment frame. The sources were not in one frame. They are in both frames. See: And the motion is entirely relevant. Each observer considers themselves as at rest - due to the relative motion they know the other observer is not at rest. That's how each observer knows the other observer is moving towards one light source and away from the other. Which is why if the strikes reach one observer at the same time, they can't reach the other observer at the same time. No, it's your logic that is circular. You are demanding absolute simultaenity, and trying to squeeze that into an experiment that shows it isn't. Again, the experiment needs to stipulate that the events are simultaneous in one frame, in order to carry that thought through and see the result. It doesn't stipulate that the events were not simultaneous in the other frame ... it shows that!

Yes, it is. Yes, he is. (That strikes happen to be simultaneous in his frame (that's what is stipulated), and not in the frame of the train). Yes, he is. It's very simple. Yes. No, in effect he does say that. The reason being that from the point of view of the embankment observer, the train observer is moving. That's what leads to the result in your text above. I've brought that to you to try to help you understand. No! If that were true, then your claims of "absolute rest" might have had some merit. Why do you think it's called "relativity of simultaneity" and not "absoluteness of simultaneity that some observers disagree with" ? What do you think he meant by "and vice versa" in the end of that section?

It's simply: all observers will agree whether events at a single location are simultaneous or not. This goes (in the train/embankment thing) to each observer agreeing whether the other observer sees the flashes at the same time. Specifically: If two flashes happen to hit the train observer at the same time, the embankment observer will agree they hit the train observer at the same time. If two flashes happen to hit the embankment observer at the same time, the train observer will agree they hit the embankment observer at the same time. This seems important to your understaning of R.O.S. No. In this particular setup, both observers consider themselves as equidistant to the flashes, and both of course can consider themselevs as at rest. If one of them (either of them!) happens to see the two flashes at the same time they can consider those flashes to be simultaneous. There is no absolute rest here, any observer (whom any other observer might consider to be "moving") can experience events that are simultaneous. No. I'm trying to help you understand the one under discussion. ... because the scenario discussed there is one where the strikes happen to be simultaneous in the embankment frame. See: http://en.wikisource.org/wiki/Relativity:_The_Special_and_General_Theory/Part_I#Section_9_-_The_Relativity_of_Simultaneity While the thought experiment is talked-through with strikes that happen to be simultaneous in the embankment frame, the result is clearly meant to apply to any frame. Think it through from the point of view of the train observer, who may consider himself as at rest. If the strikes happen to be seen at the same time by him, then they are simultaneous in his frame, and so won't be simultaneous in the embankment frame.

Well, here's my attempt: Even with relativity, some things are absolute. One of those is relative motion. While both observers can consider themselves as at rest, and the other as moving, there is no frame where both are at rest. Another is that events occurring at a single location (which equates to "an observer") will be agreed on by all (to be simultaneous or not). For example, two cars drive into a stop sign at the same time. There is no observer (whether standing "still" by the pole or "flying by" at Mach 3) who will think one car hit the sign first - there'd be no pole remaining for the other car to hit, and all observers will agree if both cars hit the pole. So if the flashes were simultaneous in the embankment frame and the equidistant embankment observer sees them at the same time, will the train observer see them at the same time? No. Because he is moving, according to the embankment observer, and light travels at a finite speed, one flash must reach the train observer before the other. And the train observer won't disagree; the flashes can't reach him at the same time in one frame, and at different times in another frame. And if the flashes were simultaneous in the train frame and the equidistant train observer sees them at the same time, will the embankment observer see them at the same time? No. Because she is moving, according to the train observer, and light travels at a finite speed, one flash must reach the embankment observer before the other. And the embankment observer won't disagree; the flashes can't reach her at the same time in one frame, and at different times in another frame. Because there is relative motion, the flashes can't reach one observer at the same time, and the other observer at the same time. But each observer (both at rest and equidistant, according to them) needs to see those flashes at the same time to consider them simultaneous. The flashes can be simultaneous in either (or neither) relatively-moving observers frame, but can't be simultaneous in both frames.

Are you going to keep asking what's essentially the same question again and again for the rest of the year? Starts to look like trolling to me.

Odd. I found http://www.compileonline.com/compile_java_online.php Copy/pasted the code from post #1 into it - and it ran first time, giving the expected result.

(re: post #7, Post#6 was more in response to post #5. For some reason certain features like Quote don't work for me in IE, and I can't always be bothered running up firefox.)

According to what I've found, a character literal in Java is written with the apostrophes, strings with quotes. In your example, that's a string being printed. In post #1, a and b are declared as char. The link in post #4 has examples of both string and character assignment.

The 'c' char literal doesn't need to be declared, it's a literal. The language knows what the letter 'c' is. (It's (more or less) 99 !) The a and b char variables do need to be declared. That's a difference between a literal and a variable. The "char a, b" is saying "I'm going to have two places to put characters, the places will be named a and b. The characters that are put into those places can be whatever characters the language knows about. So: b = 'c' : is putting the letter 'c' (which the language already knows about) into a place called a (which you declared above). But: a = b : is putting the content of the place called b into the place called a. Having had a quick google on Java syntax, I'm perplexed by the error message you are seeing. Is what you posted in post #1 exactly what you have in your code? P.S. googling for: java character literal I see: http://docs.oracle.com/javase/tutorial/java/nutsandbolts/datatypes.html ... which does seem to show apostrophes are legal syntax.

... but note it's a very bad idea, unless part of a clearly understood naming convention. For example, you might have a property named "Number" (e.g. name all properties with leading capital), and a method in the same class might have a locally scoped (meaning "visible" only inside that method) variable named "number". (This could still be a bad idea, depending on context). But you definitely wouldn't want a method that has both "Number" and "number" as locally scoped variables, or a class with both of those as properties - too easily mixed up. (Not a criticism of the preceeding example by Curiatron, which was only for illustration.)

I don't know Java, but I'd expect the intent is: 1. Put character 'b' into variable named a. 2. Put character 'c' into variable named b. 3. Put whatever is in variable b, into variable named a. (That's the diff with not having the quotes). So the three prints I'd expect to show: b c c Dunno why it won't compile for you. (What exactly is the compiler telling you?) e.g. (for comparison) this works fine in C#: using System; namespace SimpleJavaEquiv { class Program { static void Main(string[] args) { char a, b; a = 'b'; // char literal into a Console.WriteLine(a); b = 'c'; // char literal into b Console.WriteLine(b); a = b; // copy b (which is 'c') into a (overwriting its 'b') Console.WriteLine(a); // Just to pause to see result Console.ReadLine(); } } }

I guess it's true (from what I've seen on satellite T.V.) that "professional bigfoot hunters" have to stay near shops where they can buy bacon to hang from trees.

If there's a gas leak, but the question hasn't given you the rate of leak, then the problem becomes unsolvable - you'd have to invent the rate of leak, which is pointless. It's not just about simplifying the problem, it's about making it possible to solve. If you want to argue about the semantic difference between "simplification" and "making possible", well, I'm not interested in that. All problems become unsolvable if you get to invent issues not stated. How quickly will an apple fall off a 3 metre high branch? Well, I can't say, because an earthquake might occur the moment the apple drops, which causes the ground to rise at some rate, decreasing the distance the apple has to fall. Silly. Even in the real world, working on real problems, there will be simplifications in any question. You always need to determine which factors don't have enough of an effect to be worth including, and which factors are just unlikely to occur.

For a species to live, you need a certain number of them. They need to breed, and not inbreed. Take the loch ness "monster" - if there were just one, what is it? Immortal? And if it breeds how could it be so seldom seen? Same thing with bigfoot. There can't just be one, there'd have to be a population. So why so few sightings - especially now with so many cameras going out into the wilderness. Once in a while a species thought extinct is re-found, or an entirely new species is discovered, showing that animals can be "undetected". But these tend to be small, and found in largely unvisited places. Given the folk actively searching for bigfoot etc. - I don't buy their existence at all. On the OP, I'd go with - those are some very strong claims made on weak evidence. Some pretty significant further evidence would need to be found to back them up.

This all reminds me of a "story" told to me by my physics teacher, back in '86. I gather it's a common story, but don't know the details (I presume it's a myth, for illustration of a point, not based on an actual event). I won't try to tell that story in any entertaining (or accurate) way ... It involves a physics exam, and one question is along the lines of "you have a barometer; how do you measure the height of a building?". Most of the class provides an answer based on the difference in air pressure at the bottom and top of the building. Not an unreasonable assumption based on the equipment given. But this one kid gives an answer along the lines of dropping the barometer off the top of the building, and measuring the time taken. The teacher doesn't accept this as it's not the expected answer, so makes the student re-take the test. There's a whole lot more methods the kid comes up with, like unravelling his jersey and using the barometer as a weight to dangle the wool from the top of the building. I don't remember them all.

"based on no reason" seems an unfair addition too. Assumptions for a given case may be without proof (for that case), but may be based on other factors - like past experiences. For example, I've never blown up a balloon with any hole large enough to notice at the time. So given the problem in post #1 I probably wouldn't think about air escaping as the balloon was inflated. Most people, I would assume, would consider that a reasonable assumption (no hole, no air escape). It's possibly true that a cleverer person than me would have thought of that possibility, but on the other hand the experience of being given questions in a text book or exam also apply for assumptions - it'd be clear to most people what the question is asking, and that the answer is supposed to come from the parameters given - that it isn't required to make guesses about other factors, that it can be assumed there are no other factors. If you were answering that question in an exam, they didn't tell you about a hole in the balloon - so why would you invent one? And what rate of air escape would you assign it? That there is no hole seems a valid assumption, in the context of the question. I would ask, Amad27, why do you ask this question about assumptions?

Cosmic rays.

I would argue that multiplication and division are of equal precedence (they're basically the same thing) so are done left to right, in the absence of modifiers like brackets. The same goes for addition/subtraction. After all, if you really wanted to do addition before subtraction, the step 30-17+4 would come to 30-21 giving 9, not your (which I think is correct) 17. i.e. BO{DM}{AS} So ... where you show the end bit as 8*3/6 then 8*1/2 giving 4; I think that ought to be 8*3/6 then 24/6 giving (luckily the same in this context) 4. I'd show the thing, in very long form, as: 30 - (2 * 6 + 15 / 3) + 8 * 3 / 6 = 30 - (12 + 5) + 8 * 3 / 6 = 30 - 17 + 8 * 3 / 6 = 30 - 17 + 24 / 6 = 30 - 17 + 4 = 13 + 4 = 17

I'm not familiar with the term "common core"; is either of these preferred? 26 + 17 = (26 - 3) + (17 + 3) = 23 + 20 = 43 26 + 17 = (26 + 4) + (17 - 4) = 30 + 13 = 43

CaptainPanic interpreted me correctly. The plan needs twice as many runways to be built. (i.e. point 2. in post #3 is not entirely correct). (And probably much more than twice the overall airport land is needed, as all those uphill and downhill runways can't just be jumbled together and be safe for aircraft to use.) Another thought is that the "uphill landing" will require stronger landing gear, as that extra force needs to be accommodated somehow. That in turn means more weight carried - and while take off uses proportionally more fuel than cruising, many flights spend a long time cruising, so the cost of carrying that extra weight may well negate any advantage of the downhill take off. (Point 3. of post #3 missed the point.) Also, I see another safety issue in the downhill take off; if the take off doesn't go well, the plane is already headed downhill - and that downhill will soon end. At least on a flat runway, there's some chance of a less severe ending to running off the end of the runway. Not always - there's been some very horrible crashes of take off - but if the craft is already heading down hill and the hill ends soon, it'll always be worse. Sorry, the idea still makes very little sense for conventional airports. One place where it is used in part (but reversed!), is the "ski ramp" used on British aircraft carriers to helps launch Harriers. In that case it's used only for the take off. And after the end of the runway there is generally just open sea; which would be there without the ramp in place.

Aircraft get an advantage by taking off or landing into the wind; it decreases required ground speed. With your design, different runways are needed in all directions (to have an up-slope and down-slope runway into any wind direction); whereas flat runways are a suitable "average". I also don't like the idea of an aircraft landing on an up-sloping runway anyway, the approach speed in respect to the ground would start to get dangerous. (Conversely an aborted take-off on a down-sloped runway also gets harder). Sorry, I don't think the idea makes sense.

If you're gonna spend money, there are already companies that provide dedicated internet-accessed minecraft servers. You can rent one, and allow access to anyone you wish. The idea of USB connection in the OP implies "physically nearby", so just set up a small local LAN. Around here most people use a combined modem/router to access the internet, and they often have both WiFi and four Ethernet ports - so plenty of choice for interconnection. That's really the easy bit. Setting up the software for a minecraft server isn't epic, but it's not trivial either. I was looking at setting one up for my son (and his friends), before his focus moved to other games; so didn't get any actual experience in it.